Check out these clips. Back is an old 80s MTB, front is .035 and .049 4130. Platform is plywood. Front wheel is 16". Front fork is cut down 26" fork. I shot this video over the last couple of weeks. Design is from Beehive collective of Maine. I didn't make this bike because I already use a trailer, but it does make for an appealing spectacle, and can hold a beer keg or a person and their bike pretty comfortably.
The cool thing about this design as compared to similar ones is the partial re-use of junked bike tubing and the truss construction of the bottom tube. Cheaper than comparable length of 2" tubing, stronger, too.
"Hitching a ride on a cargo bike"
"Don't drink and ride"
Philly will soon be populated by about a dozen of these things. Bikes are being produced in Philly's secret apocalypse survival transportation lab. There's one on a cross country ride, too.